The inventive subject matter relates to power conversion apparatus and methods and, more particularly, to uninterruptible power supply (UPS) apparatus and methods.
UPS systems are commonly used in installations such as data centers, medical centers and industrial facilities. UPS systems may be used in such installations to provide backup power to maintain operation in event of failure of the primary utility supply.
Large data centers have proliferated with the advent of web services and cloud computing. Some newer large data centers occupy millions of square feet and house hundreds of thousands of servers. Typically powered by the local grid, these centers may include backup power supply systems including UPSs and diesel-electric backup generators to support continued operation when utility power is lost. Energy consumption is a major concern for such facilities, as some facilities are approaching the 100 MW level. For such facilities, even a few percentage points of efficiency can translate into significant expense.
Large UPS systems, such as those used in data center applications, commonly use a “double conversion” architecture wherein power is transferred via a rectifier and inverter coupled by an intermediate DC bus. Operation of such a power train can introduce losses. Accordingly, some double-conversion UPS systems support high-efficiency or “eco” modes in which the rectifier and inverter are bypassed when the input AC source meets certain criteria. Other solutions to increase data center energy efficiency, such as those described, for example, in U.S. Pat. No. 7,886,173 to Krieger et al., U.S. Pat. No. 7,560,831 to Whitted et al. and U.S. Pat. No. 8,344,546 to Sarti, include redundant power distribution techniques that avoid the use of traditional UPS architectures.